Sprocket chain guide for hoists



y I c. H. SCHRAMM 2,240,523

SPROCKET CHAIN GUIDE FOR HOISTS Filed May 31, 19:59

O Q X Patented my 6, 1941 srnooKET onAIN GUIDE FOR norsrs Christopher Henry Schramm, Muskegon, Mich assignor to Manning, Maxwell & Moore, Inc., Muskegon, Mich., a corporation of New Jersey Application May 31, 1939, Serial No. 276,495

2 Claims.

The invention pertains to portable electric hoists of the type in which the lifting, force is derived from a small electric motor and is applied to the load through the medium of a roller chain coacting with a sprocket of small diameter but having a small number of teeth of large size and pitch so as to possess the necessary strength.

In a lift mechanism of this type the chain has a tendency to leave the sprocket wheel, under gearmg, partof which is indicated at H, enclosed within the gear casing l3. A roller type chain It is reeved over the sprocket i6, with one freeend depending therefrom for hoisting a loading hook l9 attached thereto. 'The other end of said chain is fixed to the housing (as indicated at 20), with the portion of said chain between said housing'and the sprocket disposed .in'a depending loo'p 2|. A brake mechanism loaded conditions, since the load, being exerted primarily on one side of the chain, pivots on one roller causing the chain rollers on the opposite side of the sprocket to leave or carry outwardly from the sprocket. This articulation .of the chain reduces the chordal pitch and prevents the rollers from properly entering and seating them selves between the sprocket teeth. Moreover,

' the side bars of the chain, as they intermittently rise out of the sprocket, tend to hammer against any closely positioned wall such as the sprocket housing with the result that the bars become peened over and the joints of the chain become stiffened so that they will no Longer articulate properly.

With the foregoing in view the object of the "invention is to provide new and improved means for guiding the lifting chain as it passes over the sprocket so as to insure proper entrance of the chain rollers between -thc sprocket teeth in the operation of lifting heavy loads.

I Further objects and advantages'of the invention will become apparent as the following detailed description proceeds taken in connection with the accompanying drawing, in which:

Figure 1 is a general perspective view of a hoist embodying the features of the invention.

Fig. 2 is an enlarged partial vertical longitudinal section through the lower portion of the hoist shown in Fig. 1'. i

Fig. 3 is a vertical sectional view taken along line iii-d of Fig. 2.

Figs. 4 and 5 are enlarged detail perspective views of a chain guide and a stripper, respectiveiy.

' For purposes of exempliflcation of the inventlon, it has been shown herein as embodied in a small portable hoist (Fig. 1). Toidentlfy the lower side of the sprocket it is embraced by a 22 and a reversing controller 23, operated by a pair of control cords 24 and 25, are secured to the outer end and tothe lower side of the motor, respectively. It should be understood that the general arrangement and form of the hoist parts described above constitute no part of the present invention. I

Turning to a more detailed description of the sprocket housing M and its associated parts (Figs. 2 and 3) which form a background for the present invention, the housing itself cornprises an extension 26 open at the bottom and integral with the lower portion of the inner face of the gear casing l3. Thechain sprocket it in the present instance is formed integrally with a supporting stud shaft 21 driven by the gearing ill and journaled in a conventional ball bearing 2d at its free end and in a suitable sleeve bearing 23 fitted in the inner end of the housing it. "The open end of the extension 26 is closed by a cover plate 39 bolted thereto, as at 3!. The

1 block 32 (Figs. 2, 3 and 5) of generally U-shaped cross section suitably secured to the open bot-. tom of the extension, as by bolts 33. This block 32 forms a partial closure for the bottom of the sprocket housing M and, in addition, prevents the chain from wrapping around the sprocket I by stripping the former from the latter, when general elements of the hoist selected for illustration of the invention, it includes an electric motor it, a reduction gear casing l3, and a sprocket housing It, mounted as a unit and adapted to be supported by a hook l5. The motor it drives a rotatable chain sprocket 16 (Fig. 2) through the medium of a speed reduction in operation. 7

- The chain disclosed herein is of a conventional type, comprising a series of spaced parallel rollers 35 interconnected by side bars 36. The side bars are pivotally connected to each other and to the ends of the rollers, as indicated at 3?, to provide for conventional chain articulation at these points. i

The sprocket i6 has a-plurality of teeth-38 over which the chain is reeved, and is made of relatively small diameter in order to reduce the power requisite to overcome the torque exerted by the loaded chain on one side of the sprocket. Moreover the number of teeth is relatively small to obtain. the desired strength in the individual teeth-five teeth being herein shown. In this connection it will be appreciated that the-previously described diificulty of chaindisplacement,

Q large size and pitch. At the same time proper encaused by the chain pivoting on one roller and thereby resulting in succeeding rollers rising out of their normal seated. position between the sprocket teeth, is materially increased where a sprocket having a small number of large pitch teeth is employed. This is because there are not a sufficient number of teeth-in fact, possibly only one tooth-4n simultaneous contact with the chain and in support of the load to prevent undue pivoting of the unloaded rollers.

To insure the maintenance of proper running engagement between the chain and its sprocket, I have provided a chain guide means fashioned to engage the rollers independently of the side bars of the chain when the latter moves outwardly beyond permissible limits. One embodiment of such a guide (illustrated in Fig. 4) comprises a generally U-shaped hardened strap 39 having a smooth inner surface 40 to provide an arcuate bearing surface over which the rollers may travel.

Inthe present instance, as seen in Figs. 2'and 3, the guide is removably secured in the housing M, by bolts 4i and a dowel $2, in an inverted position so that it straddles the sprocket with its legs extending downwardly to a position below the sprocket. The bearing surface 40 of the guide is disposed circumferentially of the sprocket (Fig. 2) and concentric with the path of travel .of the chain rollers over the sprocket. Preferably the surface 4!] is spaced a short distance from the tips of the sprocket teeth for smoothness in operation, butis adapted to be engaged by the chain rollers to prevent any undesirable displacement of th chain under the load. It will be seen that the guide. is disposed between the planes of the opposed side bars of the chain so that the bearing surface 4!) engages the rollers intermediately of said planes without contacting the side bars.

In operation, the chain It enters the sprocket l6 and the rollers 35 are seated between the sprocket teeth 38. Upon any undue rising tendency of the rollers from their seated position, they will bear against and travel over the surface All of theguide concentric with their normal path of travel over the sprocket and their position between the sprocket teeth will be maintained witliout any contact between the side bars 36 of the chain and the guide.

It will be seen that the construction provided contributes substantially to the operation of a small portable electric hoist. It permits of the use of a chain sprocket of the small size required for maximum utilization of the driving force of a gagement between the chain and sprocket is insured thus promoting smoothness of operation as well as prolonging the life of the lifting mechanism.

I claim as my invention:

1. A portable electric hoist comprising, in com-' bination, a frame structure, a shaft journaled for rotation in said frame structure, an electric motor in driving relation with said shaft, a chain sprocket fixed forarotation with said shaft, a roller type chain reeved over said sprocket and disposed with one end depending therefrom for supporting a load, the other end of said chain being secure'd to said frame structure with the portion of said chain between said structure and said sprocket disposed in a depending loop, said chain embodying spaced'rollers interconnected by opposed sets of articulated side bars, and an arcuate chain guide rigid withsaid frame structure and disposed to provide a bearing surface circumferentially spaced from the path of travel of the rollers over the sprocket, said bearing surface being positioned between the opposed sets of side bars, whereby to engage the rollers intermediately of said sets to prevent unreeving of the chain upon any tendency of the rollers to move out of small or fractional horse power electric motor and this, even though the sprocket teeth are of engagementwith the sprocket teeth when the chain is'under load. v

2. A portable electric hoist capable of liftinglarge loads with a relatively small capacity electric power unit, said hoist comprising, in combination, ahousing, arotatable chain sprocket j ournale'd in said housing and having a small number of teeth of large size and pitch, means including an electric motor for driving said sprocket, a

roller type chain reeved over said sprocket with one end depending from one side of said sprocket through the bottom of said housing for supporting a load, the portion of said chain on the other side of said sprocket being free for unloaded running engagement withsaid sprocket, said chain having spaced rollers interconnected by side bars, the diameter of said rollers being less than the width of said side bars, stationary chain guide means for holding said chain in running engagement with said sprocket while under load, said means comprising a U-shaped member secured in said housing in a position straddling said sprocket and concentrically spaced from the perimeter of the upper and side portions thereof and having a width less than the length of said rollers whereby to prevent movement of said rollers out of engagement with said sprocket by engagement with said rollers only.

CHRISTOPHER HENRY SCHRAMM. 

